The proposed case-control study is a population-based investigation of dietary factors and the development of non- Hodgkin's lymphoma (NHL) in adults. Selected dietary factors of primary interest include animal protein, total fat, unsaturated fats (specifically, omega-6 fatty acids), and Vitamin A. Incident cases of NHL will be identified through the population- based Cancer Surveillance System (CSS) of the Fred Hutchinson Cancer Research Center (FHCRC). Eligible persons will be 20-64 years of age, residents of the tri-county area surrounding Seattle (King, Pierce, and Snohomish counties), and diagnosed between June 1, 1988 and May 31, 1989. An equal number of controls will be randomly chosen residents of the same tri-county area and frequency matched to the cases by sex and 5-year age categories. Information on past dietary practices will be collected from all study subjects (three years before diagnosis/reference date) using a modification of the self-administered dietary history questionnaire developed at the National Cancer Institute. This instrument will utilize dietary intake data from the Second National Health and Nutrition Survey (NHANES II) to obtain representative intake levels of selected nutrients as well as frequency of consumption information. In addition, a telephone interview will be conducted to obtain necessary socio- demographic, occupational, and lifestyle data which may confound the dietary variables of interest. The results of the investigation will: 1) provide epidemiologic evidence regarding the role of dietary constituents and the development of NHL; 2) provide preliminary indications of disease mechanisms inferred from resulting nutrient-specific findings; and 3) provide indications for further research of NHL in the future.